1. Field of the Invention
This invention relates to a hydrogen gas visualization device for visualizing the existence of hydrogen gas in an atmosphere to allow it to be recognized by the eye or the like.
2. Description of the Related Art
In order to suppress the emission of carbon dioxide, attention is given to hydrogen as an energy source. If, however, hydrogen gas leaks into an atmosphere around a device using hydrogen as an energy source (automobile using hydrogen-fuel cells, for example) or the like (atmosphere at a basement car park, a hydrogen gas station or the like), an explosion may happen. Thus, it is necessary to quickly detect and stop the leakage of hydrogen gas. It is however not practical to detect the hydrogen gas leaked into the atmosphere using the Schlieren method, the PIV method and the like, which are gas detection methods for use in laboratories and the like. In the first place, these methods can detect a convective flow of gas but cannot selectively detect hydrogen gas among other gases.
Thus, a leaked hydrogen gas detection device employing a semiconductor sensor using tin oxide capable of selectively detecting hydrogen gas in an atmosphere has been devised.
Further, switchable mirror glass which selectively reacts to hydrogen gas in the manner such that a thin film layer formed on the glass surface is hydrogenated at room temperature (around 20° C.) under the action of a catalyst layer and comes into a transparent state, and is dehydrogenated in the temperature range of the room temperature to 100° C. and comes into a mirror state is proposed in Japanese Unexamined Patent Publication No. 2003-335553 (hereinafter referred to as “patent document 1”), Japanese Unexamined Patent Publication No. 2004-139134 (hereinafter referred to as “patent document 2”), etc.
Such switchable mirror glass is applied to windows in buildings and automobiles to perform light control by changing the optical transparency of the glass almost uniformly across the entire glass surface, using hydrogen gas.
Further, a detection device which, by using a hydrogen sensor including a thin film layer formed on the surface of a substrate such as a glass or vinyl sheet, capable of being quickly hydrogenated under the action of a catalyst layer and thereby changing in optical reflectance, can detect the existence of hydrogen gas at a location where the hydrogen sensor is placed is proposed in Japanese Unexamined Patent Publication No. 2005-83832 (hereinafter referred to as “patent document 3”).
In order to, however, prevent the leaked hydrogen gas from causing an explosion, quick detection of the leakage is not enough. It is necessary to quickly identify the source from which the hydrogen gas leaks and stop the leakage of the hydrogen gas. For this purpose, it is necessary to be able to detect the existence and flow of the leaked hydrogen gas across a relatively large region, safely and quickly, and determine the leakage source from the flow of the leaked hydrogen gas.
The semiconductor sensor using tin oxide capable of selectively detecting hydrogen gas, however, operates at relatively high temperature around 400° C. and therefore needs a heating device. Thus, if such semiconductor sensor is applied to a leaked hydrogen gas detection device, the possibility of the heating device inducing an explosion of leaked hydrogen gas cannot be denied. Further, since a power source is required to operate the semiconductor sensor, the possibility of failure of a power-source device or the like inducing an explosion of leaked hydrogen gas cannot be denied. There is also a problem that if a disaster or the like causes a power outage, the operation of the hydrogen gas detection device stops. Further, the above-mentioned hydrogen gas detection device only detects the existence of leaked hydrogen gas at a location where the semiconductor sensor is placed, and cannot quickly detect a flow of leaked hydrogen gas across a relatively large region and therefore cannot quickly identify the leakage source from which hydrogen gas leaks.
Further, the above-mentioned switchable mirror glass (patent documents 1 and 2) selectively reacting to hydrogen is intended to be changed in optical transparency by hydrogen gas almost uniformly across the entire glass surface, and therefore not suited to quickly detect a flow of leaked hydrogen gas across a relatively large region.
Further, the hydrogen sensor with a catalyst layer formed on the surface of a substrate of glass or the like (patent document 3) only detects the existence of hydrogen gas at a location where the sensor is placed. It cannot visualize the existence and flow of hydrogen gas in an atmosphere.